1. Field of the Invention
The present invention relates to a mirror support mechanism that supports a mirror integrated in a telescope in such a way as to prevent a mirror surface accuracy from being degraded by the deformation of the mirror, and an optical apparatus using the same.
2. Description of the Related Art
A mirror support mechanism in a conventional telescope is described in a non-patent document 1. According to FIG. 4. 24 (page 290) and description corresponding to the drawing in this non-patent document 1, a whiffle-tree support mechanism is disclosed as a support in the axial direction of a main mirror. In this whiffle-tree support mechanism, spherical seats are provided at three fixed points and a trifurcate pole is placed on each of these spherical seats and nine pads of the main mirror are placed on the top of the trifurcate pole via spherical seats. The trifurcate pole is made freely incline along the back of the main mirror by the spherical seats provided at the fixed points, whereby the nine pads of the main mirror are arrayed in the same plane. By this arrangement of support mechanism it is prevented that the harmful deformation due to the internal stress of the support mechanism for the main mirror is transmitted to the main mirror.
[Non-patent document 1] Reflecting Telescope, by Yasumasa Yamashita, 4.2.1 Position Control and Force Control of Mirror, p287–p291, published by University of Tokyo Press, 1992.
In optical telescopes or radio telescopes for making astronomic observation or the like in recent years, there has been a tendency to increase its size of main mirrors for the purpose of improving a resolving power and making more accurate observation. In a large size telescope like this, the main mirror is made of one mirror panel or a plurality of mirror panels, and in the case of constructing the telescope with one main mirror, a technology has been employed in which the main mirror is actively driven to make the mirror surface is adjusted in order to correct the deformation of main mirror caused by temperature distribution or inclination by gravity. And in the case where the main mirror is made of a plurality of mirror panels to form one main mirror as a whole, in order to adjust the position in the direction of a mirror axis and the inclination of each mirror panel, a technology for actively driving the mirror panels has been employed. According to the conventional mirror support mechanism disclosed in the non-patent document 1, a technology of using a plurality of mechanical parts such as spherical seats in a passive support structure, is disclosed. However, if an active driving mechanism is added to this passive structure and the main mirror or the individual mirror panels are intended to drive, there is presented a problem that the bandwidth of drive control cannot be maintained in wide area because of backlash in the mechanical parts in the support structure and the low rigidity of the support structure. In addition, there is also presented a problem that as the main mirror is increased in size and the number of mirror panels are increased, number of parts are drastically increased to make its cost expensive in the conventional support structure and at the same time, an increased number of parts makes the structure complicated and accuracy degraded in manufacturing and assembling.